Top seed Djokovic labored for two hours to win 6-3, 4-6, 6-3 against German qualifier Dominik Koepfer.
Also absent were midfielder Arthur Melo, who joined Juventus from Barcelona in July, Flamengo striker Gabriel Barbosa and Real Madrid left-back Marcelo. Sao Paulo's defender-turned-midfielder Dani Alves is unavailable because of a fractured forearm.
The 22-year-old Osaka outlasted an inspired Victoria Azarenka from Belarus 1-6, 6-3, 6-3 in the US Open final on September 12 to clinch her second US Open title and third Grand Slam, following her victories in the 2018 US Open and 2019 Australian Open.
The Arsenal captain scored a brace in last season's FA Cup final as Arsenal came from behind to beat Chelsea 2-1. He also netted in Arsenal's 3-0 victory over Fulham last Saturday in their first game of the new Premier League season.
Reguilon broke into the Real Madrid first team in the 2018-19 season, making 22 appearances and moving ahead of the Brazilian left back Marcelo in the pecking order.
To secure his club's place in the Bundesliga and to make the Belgian Euro 2021 squad are his main goals for the upcoming season.
Zhou, 22, drew 2-2 with compatriot Zhao Jianbo and Ricky Walden, but a 3-0 victory over Gerard Greene secured him top spot in the group.
Li Jialun of Heilongjiang competes during the Men's High Jump Final on Day 2 of the 2020 Chinese National Athletics Championships in Shaoxing, east China's Zhejiang Province, Sept. 16, 2020. (Xinhua/Wang Lili)
The "Bulls" staged a powerful start on home turf and pressed the "Nullfunfer" onto the back foot.
Fourth-seeded Matteo Berrettini outlasted Stefano Travaglia 7-6 (5), 7-6 (1) in an all-Italian contest to reach the last eight.
Elsewhere, Eintracht Frankfurt shared the spoils with newly-promoted Arminia Bielefeld following a 1-1 draw. Augsburg downed Union Berlin 3-1 with two late goals, while Freiburg secured a 3-2 victory over newly-promoted Stuttgart. Enditem